Thermal Stress Reduction for Heat Exchanger

ABSTRACT

A heat exchanger with a first manifold and a second manifold. The heat exchanger includes tubes having first and second ends. The tubes connect to the first manifold at the first end and the second manifold at the second end establishing fluid communication between the manifolds. The tubes are arranged parallel and forming gaps between tubes. The heat exchanger includes fin matrices formed from fins that span the gaps and extend from the first end to the second end. At least two adjacent tubes define an expansion gap that accommodates thermal expansion.

TECHNICAL FIELD

This patent disclosure relates generally to a heat exchanger and, more particularly, to a heat exchanger in which thermal energy from fluid in a plurality of tubs is transferred to the surrounding environment.

BACKGROUND

Heat exchangers are used in a variety of applications to transfer heat from one medium to another. Commonly, heat exchangers are used to cool a fluid for reuse in the same process or application that initially heated that fluid. For example, an internal combustion engine may be associated with a heat exchanger to cool a fluid coolant that has been circulated through the engine to remove heat generated by the internal combustion process. In an internal combustion engine, the generated heat is normally transferred the surrounding environment.

One problem associated with heat exchangers arises from the thermal expansion and contraction of materials and the fact that, by design, heat exchangers transfer thermal energy between circuits or regions at different temperatures. The thermal difference may cause non-uniform dimensional changes to the interconnected parts of the heat exchanger. These dimensional changes can lead to rupture or failure of the parts of the heat exchanger. One approach to mitigating the problem of thermal stress buildup in heat exchangers is described in U.S. Application Publication 2003/0106677 (“the '677 publication”) titled “Split Fin for a Heat Exchanger.” The '677 publication describes using heat flow interrupters for thermal stress reduction defined by a slit extending completely through a fin and characterized by the absence of the removal of any material of which the fin is made at the slit.

SUMMARY

The disclosure describes, in one aspect, a heat exchanger comprising a first manifold and a second manifold. The heat exchanger also includes a plurality of tubes having a first end and a second end. The tubes are connected to the first manifold at the first end and connected to the second manifold at the second end such that fluid communication is established between the first manifold and the second manifold. The plurality of tubes are arranged parallel to and aligned with each other forming a plurality of gaps between adjacent. The heat exchanger also includes a plurality of fin matrices formed from a plurality of fins. The fin matrices span the plurality of gaps and extend from the first end to the second end of the tubes. Additionally, at least two adjacent tubes define at least one expansion gap that accommodates thermal expansion of the plurality of tubes.

In another aspect, the disclosure describes an internal combustion engine comprising a heat exchanger. The heat exchanger includes a first manifold and a second manifold. The heat exchanger also includes a plurality of tubes having a first end and a second end. The tubes are connected to the first manifold at the first end and connected to the second manifold at the second end such that fluid communication is established between the first manifold and the second manifold. The plurality of tubes are arranged parallel to and aligned with each other forming a plurality of gaps between adjacent tubes. The heat exchanger also includes a plurality of fin matrices formed from a plurality of fins. The fin matrices span the plurality of gaps and extend from the first end to the second end of the tubes. Additionally, at least two adjacent tubes define at least one expansion gap that accommodates thermal expansion of the plurality of tubes.

In further aspect, the disclosure describes a method of manufacturing a heat exchanger. The method includes arranging a plurality of tubes parallel and aligned with each other. The plurality of tubes forms a plurality of gaps between adjacent tubes. The method also includes assembling a plurality of fin matrices in a plurality of the gaps formed between adjacent tubes, and assembling at least one spacer in at least a portion of at least one gap. The method also includes arranging the plurality of tubes between a first manifold and a second manifold such that fluid communication is created between the first manifold and the second manifold through the plurality of tubes. The method includes coating at least the fin matrices with a braze material, and heating at least the braze material to at least a first predetermined temperature. The method also includes removing the at least one spacer from the at least one gap, forming at least one expansion gap defined by at least two adjacent tubes. The expansion gap accommodates thermal expansion of the plurality of tubes.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view of a prior art heat exchanger including a plurality of tubes extending between a first manifold and a second manifold.

FIG. 2 is a front view of the prior art heat exchanger of FIG. 1 with the plurality of tubes in thermal expansion.

FIG. 3 is a front view of a heat exchanger in accordance with the present disclosure.

FIG. 4 is a front plan view of the heat exchanger of FIG. 3 in accordance with the present disclosure.

FIG. 5 is a flow chart illustrating a manufacturing process of a heat exchanger in accordance with the present disclosure.

FIG. 6 is a perspective view of another embodiment of a heat exchanger in accordance with the present disclosure.

FIG. 7 is a partial perspective view of the heat exchanger of FIG. 6.

FIG. 8 is a partial front view of the heat exchanger of FIG. 6.

DETAILED DESCRIPTION

This disclosure relates to heat exchangers for exchanging heat between two or more mediums, typically fluids. Although the specific examples of heat exchangers described herein are typically intended for use with internal combustion engines, heat exchangers in accordance with the disclosure can more broadly be used in any appropriate application or process such as heating and cooling applications, energy production, chemical and material processing, etc. The specific heat exchangers described herein typically function by transferring heat from a first fluid circulating inside the heat exchanger to a second fluid, such as atmospheric air surrounding and flowing over the surfaces of the heat exchanger. The transfer mechanism is commonly referred to as convection although the specific details of the thermodynamic transfer mechanism should not be considered a limitation on the claims. In some embodiments, the process may be reversed so that heat from the surrounding environment is transferred to the fluid circulating in the heat exchanger to raise its temperature.

Referring to FIG. 1, wherein like reference numbers refer to like elements, there is illustrated a prior art example of a heat exchanger 10 that may be used with a process, such as in connection with an internal combustion engine. The heat exchanger can be used in positive pressure fuel injected systems to cool fuel returning from the fuel injector circuit, or in any other appropriate cooling application to cool engine coolant or lubricating oil returning from the engine block. To channel the fluid to be cooled, the heat exchanger 10 includes a plurality of hollow, elongated tubes 12 that can be arranged longitudinally, spaced apart, and parallel to each other in what may be referenced as a tube core 14. A plurality of gaps 15 are formed between each adjacent tube 12. The tubes can extend between and be in fluid communication with a first manifold 16 and a second manifold 18. The first manifold 16 can function as an intake manifold receiving heated fluid from the process and the second manifold 18 can function as an outlet manifold returning the cooled fluid to the process. The fluid can flow between the tubes in a direction 19 indicated in FIG. 1. To promote cooling, the heat exchanger 10 can include surface area increasing fin matrices 20 in the gaps 15. Each fin matrix 20 is comprised of a plurality of individual fins 21 that can be connected to the walls of the tubes 12 by brazing, welding, or other connecting methods. The fins 21 can help dissipate heat from the fluid in the tubes 12 into the environment as the fluid flows from the first manifold 16 to the second manifold 18.

A problem arising with the prior art heat exchanger 10 is that the tubes 12 may undergo thermal expansion and contraction due to the fluids circulating therein. For example, the parallel tubes 12 may increase in length while the ends of the tubes remain in a fixed position relative to the first manifold 16 and the second manifold 18, causing the tubes to expand laterally in a direction 23 substantially perpendicular to the fluid flow. FIG. 2 illustrates the prior art heat exchanger 10 as the tubes 12 in the tube core 14 undergo lengthening as a result of thermal expansion. The tubes 12 at the very outer ends 24 of the tube core 14 are adjacent to only one other tube in a lateral direction, whereas the other tubes closer to the tube core center 22 are laterally adjacent to two other tubes. As a result, and as shown in FIG. 2, the tubes 12 at the center 22 of the tube core 14 are more constrained such that they exhibit only slight lateral bending with the thermal expansion, while the distance of lateral tube bending increases with proximity to the outer ends 24 of the tube core to accommodate both the outer tube expansion and the expansion of the inner tubes. It should be understood that the degree of bending shown in FIG. 2 may be exaggerated for descriptive purposes. Large degrees of expansion of the tubes 12 can result in thermal and mechanical stresses that, when repeated, may lead to metal fatigue. These stresses can concentrate in stress regions 40 located proximate to the joints and attachment points between the tube core 14 and the first and second manifolds 16, 18. If severe enough, the thermal stresses can cause the joints and/or attachment points to fracture or rupture leading to failure of the heat exchanger. An increased number of tubes 12 in the tube core 14 exacerbates the problem due to the greater degree to which the outer tubes must accommodate the expansion of the large number of inner tubes.

Referring now to FIG. 3, there is illustrated a heat exchanger 100 in accordance with the disclosure that can better accommodate the thermal expansion of the tubes to mitigate the effect of thermal and mechanical stress. To establish fluid communication between the heat exchanger 100 and an associated process or application 200, the heat exchanger can include a first manifold 116 and a second manifold 118 connected to a plurality of elongated tubes 102. The first manifold 116 can function as an intake manifold receiving heated fluid from the process or application 200 and directing it to the tubes 102, and the second manifold 118 can function as an outlet manifold receiving the cooled fluid from the tubes 102 and returning it to the process or application 200. The process or application 200 can be any suitable application that can benefit from fluid cooling, such as an internal combustion engine. The first and second manifolds 116, 118 can include suitable fittings (not shown), such as threaded hose fittings, to physically connect hose lines or other connecting conduit 202, 204 from the associated process to the first and second manifolds 116, 118.

The plurality of tubes 102 are arranged substantially in parallel and spaced apart from each to form a tube core 110. To channel or direct fluid within the tube core 110, the tubes 102 are hollow and can be made from thin-walled material such as aluminum or another suitable metal. The tubes 102 can connect to the first manifold 116 at a first end 104, and can connect to the second manifold 118 at a second end 106. The plurality of tubes 102 can be aligned along their longitudinal direction 108 and their lengths are such that the first ends 104 coextensively align together and the second ends 106 coextensively align together. The tube core 110 therefore has a generally rectangular shape, with the first and second manifolds 116, 118 generally perpendicular to the plurality of tubes 102 and perpendicular to the longitudinal direction 108 of the tubes. It is contemplated that some embodiments include multiple rows of tubes 102, for example, at least a second row positioned behind and parallel to the tubes shown in the embodiment in FIG. 3.

Fluid can circulate through the heat exchanger 100 by entering the first manifold 116 via an intake conduit 202, passing longitudinally through the tubes 102, and exiting the second manifold 118 via an outlet conduit 204. Air or another medium moving or flowing across and perpendicular to the tube core 110 can pass through the spaced-apart tubes 102, while absorbing heat by convection and transferring the absorbed heat away from the heat exchanger 100. A gap 105 is formed between each pair of adjacent, spaced-apart tubes 102, forming a plurality of gaps throughout the tube core 110. To facilitate heat transfer by increasing the surface area available for cooling, fin matrices 120 are included in at least a plurality of the gaps 105 between the spaced-apart tubes 102 and may extend between the first and second manifolds 116, 118. Each fin matrix 120 can be comprised of a plurality of individual fins 121 that can be connected to the walls of the tubes 102 and/or to one another by brazing, welding, or other connecting methods. The fin matrices 120 and fins 121 can be formed from thin-walled corrugated metal undulating between adjacent tubes 102.

To accommodate or militate against thermal cycling, the resulting dimensional changes, and thermal stress buildup, the heat exchanger 100 can be designed so that the tubes 102 can more freely expand along an axis 122 substantially perpendicular to their longitudinal direction 108. One way this can be accomplished is by including at least one expansion gap 130 in the tube core 110. An expansion gap 130 is a gap 105 in which at least a portion of the gap contains no fins 121 between the pair of adjacent tubes 102. The embodiment illustrated in FIG. 3 includes two expansion gaps 130, dividing the tube core 110 into three tube sets: a first tube set 124, a second tube set 126, and a third tube set 128. Each tube set is separated by an expansion gap 130. Although the embodiment illustrated in FIG. 3 shows two expansion gaps 130 and three resulting tube sets, different embodiments can include different quantities of expansion gaps 130 and tube sets. Additionally, while FIG. 3 shows the two expansion gaps 130 with partial fin matrices 132 with fins 121 positioned only adjacent the first manifold 116 and second manifold 118, it is contemplated that the expansion gaps can include no fins at all in some embodiments. Moreover, although each tube set in the illustrated embodiment includes substantially the same number of tubes 102, it is contemplated that each tube set can each include different numbers of tubes 102.

FIG. 4 illustrates a possible benefit provided by the disclosure in including expansion gaps 130 in the heat exchanger 100. The heated fluids circulating throughout the heat exchanger 100 and through the tube core 110 can cause the tubes 102 to undergo thermal expansion. For example, the tubes 102 may increase in length, causing the tubes to bend between the first and second manifolds 116, 118, expanding laterally substantially parallel to axis 122. As shown in FIG. 4, because the expansion gaps 130 are mostly free of fins 121, the tubes 102 are able to expand into the expansion gaps between adjacent tube sets. It should be understood that the degree of bending shown in FIG. 4 may be exaggerated for descriptive purposes. The allowance for expansion provided by the expansion gaps 130 effectively transforms the larger tube core 110 into three, smaller tube cores each comprising a tube set 124, 126, or 128, each with fewer tubes 102 than the tube core 110 itself. In such an embodiment, the tubes 102 at outer ends 134 of the tube core 110 need not accommodate the entire expansion of the tubes 102 nearer to the center 136 of the tube core, as is the case with the prior art heat exchanger 10 discussed above. Instead, the expansion gaps 130 accommodate expansion of the tubes 102 adjacent the expansion gaps 130, which reduces the expansion of all the tubes in the tube core 110. As a result, the smaller amount of thermal expansion in the tubes 102 results in lesser thermal and mechanical stresses that can damage the tubes 102. Using the disclosed heat exchanger 100, therefore, enables use of large heat exchangers that include large quantities of tubes while limiting the risk of mechanical failure due to thermal expansion.

As also shown in FIG. 4, some embodiments include partial fin matrices 132 proximate the first manifold 116 and the second manifold 118 in the expansion gaps 130. The partial fin matrices 132 can fill at least a portion of the expansion gaps 130, limiting the thermal expansion that takes place at stress regions 140 located proximate to the joints and attachment points between the tubes 102 and the manifolds 116, 118. In such an embodiment, the expansion gaps 130 accommodate tube 102 expansion to reduce mechanical stresses, but the partial fin matrices 132 limit the risk of damage to the tube material at stress regions 140 by limiting thermal expansion at those stress regions. The partial fin matrices 132 can limit expansion thermally as a result of the heat dissipation provided by the partial fin matrices 132 at the joints between the tubes 102 and the manifolds 116, 118, and limit expansion physically by providing physical resistance to tube expansion in the direction of the partial fin matrix 132.

Referring now to FIG. 3 and FIG. 5, there is illustrated a flow chart of a method 300 of manufacturing an embodiment of the heat exchanger 100 in accordance with the disclosure. After starting at 301, the method includes arranging the plurality of tubes 102 parallel and aligned with each other at 302, forming a plurality of gaps 105 between adjacent tubes 102 and at least one expansion gap 130. The method 300 also involves assembling the plurality of fin matrices 120 in the plurality of gaps 105 between adjacent tubes at 303, and assembling at least one spacer in at least a portion of the expansion gap 130 at 304. The plurality of tubes 102 is then arranged at 305 between the first manifold 116 and the second manifold 118 such that fluid communication is created between the first manifold 116 and the second manifold 118 through the plurality of tubes 102. At 306, the fin matrices 120 are coated with braze material, while the spacers in the expansion gaps 130 are not coated with braze material. The braze material can be any material known in the art, such as metal alloy, that is suitable for brazing in the particular process or application 200. The chosen braze material can have a melting temperature lower than that of the material making up the fin matrices 132 and the plurality of tubes 102. The method 300 also includes heating the braze material at 307 to a first predetermined temperature. The first predetermined temperature should be at least as high as the melting point of the braze material to allow the braze material to wet the fin matrices 120 and adjacent tubes 102 without melting the fins or tubes themselves. In some embodiments, the braze material is allowed to cool at 308 below a second predetermined temperature. The second predetermined temperature can be a temperature below the melting point of the braze material. At 309, the method 300 includes removing the spacers from the expansion gaps 130, leaving at least a portion of the expansion gap 130 free of any fin matrices. Other brazing methods known in the art are also contemplated herein.

In certain embodiments, the plurality of tubes 102, fin matrices 120, and spacers are assembled by alternatively stacking tubes and fin matrices in a suitable container until the desired number of tubes 102 is assembled to construct the heat exchanger 100. When a point during assembly is reached where an expansion gap 130 desired between adjacent tubes 102, a spacer can substitute for a fin matrix 120. In some embodiments, fin matrices 120 can serve as spacers in the expansion gaps 130 during assembly. In such embodiments, the fin matrices 120 used as spacers to fill the expansion gaps 130 are not coated with braze material. As a result, after the braze material is heated and cooled, the fin matrices 120 in the expansion gaps can be removed, while the fin matrices 120 in the plurality of gaps 105 that were coated in braze material remain in place between the tubes 102.

Referring now to FIG. 6, FIG. 7, and FIG. 8, there is illustrated another embodiment of a heat exchanger 400 in accordance with the disclosure that can better accommodate the thermal expansion of the tubes to mitigate the effect of thermal and mechanical stress. To establish fluid communication between the heat exchanger 400 and an associated process or application, the heat exchanger can include a first manifold 416 and a second manifold 418 connected to a plurality of elongated tubes 402. The first manifold 416 can function as an intake manifold receiving heated fluid from the process or application and directing it to the tubes 402, and the second manifold 418 can function as an outlet manifold receiving the cooled fluid from the tubes and returning it to the process or application. The process or application can be any suitable application that can benefit from fluid cooling, such as an internal combustion engine. The first and second manifolds 416, 418 can include suitable fittings 417, 419, such as threaded hose fittings, to physically connect hose lines or other connecting conduit from the associated process to the manifolds.

The plurality of tubes 402 are arranged in parallel and spaced apart from each to form a tube core 410. To channel or direct fluid within the tube core 410, the tubes 402 are hollow and can be made from thin-walled material such as aluminum or another suitable metal. The tubes 402 connect to the first manifold 416 at a first end 404, and connect to the second manifold 418 at a second end 406. The plurality of tubes 402 can be aligned along their longitudinal direction and their lengths are such that the first ends 404 coextensively align together and the second ends 406 coextensively align together. The tube core 410 therefore has a generally rectangular shape, with the first and second manifolds 416, 418 generally perpendicular to the plurality of tubes 402 and perpendicular to the longitudinal direction of the tubes.

Fluid can circulate through the heat exchanger 400 by entering the first manifold 416 via an intake conduit (not shown), passing longitudinally through the tubes 402, and exiting the second manifold 418 via an outlet conduit (not shown). Air or another medium moving or flowing perpendicular to the tube core 410 can pass through the spaced-apart tubes 402, absorbing heat by convection and transferring the absorbed heat away from the heat exchanger 400. A gap 405 is formed between each pair of adjacent, spaced-apart tubes 402, forming a plurality of gaps throughout the tube core 410. To facilitate heat transfer by increasing the surface area available for cooling, fin matrices 420 are included in at least a plurality of the gaps 405 between the spaced-apart tubes 402 and may extend between the first and second manifolds 416, 418. Each fin matrix 420 can be comprised of a plurality of individual fins 421 that can be connected to the walls of the tubes 402 and/or to one another by brazing, welding, or other connecting methods. The fin matrices 420 and fins 421 can be formed from thin-walled corrugated metal undulating between adjacent tubes 402 conveying the heated fluid. It should be understood that, although the fins 421 making up the fin matrices 420 are not explicitly shown in FIG. 6 for purposes of clarity, the gaps 405 illustrated in FIG. 6 can include fin matrices as disclosed and further illustrated in FIGS. 7 and 8.

To accommodate or militate against thermal cycling, the resulting dimensional changes, and thermal stress buildup, the heat exchanger 400 can be designed so that the tubes 402 can more freely expand along an axis perpendicular to their longitudinal direction. One way this can be accomplished is including at least one expansion gap 430 in the tube core 410. An expansion gap 430 is a gap 405 in which at least a portion of the gap contains no fins between the pair of adjacent tubes 402. The embodiment illustrated in FIG. 6 includes two expansion gaps 430, dividing the tube core 410 into three tube sets: a first tube set 424, a second tube set 426, and a third tube set 428. Each tube set is separated by an expansion gap 430. Although the embodiment illustrated in FIG. 6 shows two expansion gaps 430 and three resulting tube sets, different embodiments can include different quantities of expansion gaps and tube sets. Moreover, it is contemplated that each tube set can each include any number of tubes.

INDUSTRIAL APPLICABILITY

The present disclosure is applicable to heat exchangers in general and particularly to heat exchangers that cool a process fluid heated by an associated application such as an internal combustion engine and that returns the fluid to the application. Referring to FIG. 3, heated fluid can be introduced to the heat exchanger 100 through the first manifold 116 that distributes the fluid to a plurality of tubes 102 extending across a tube core 110. The fluid is cooled as it is directed through the tubes 102 and the cooled fluid is received by the second manifold 118 that can return it to an application 200, such as an internal combustion engine. The tubes 102 and the first and second manifolds 116, 118 can be arranged and interconnected in a manner to accommodate thermal expansion occurring in the components of the heat exchanger 100. For example, the tube core can be divided into tube sets separated by an expansion gap. In such an embodiment, partial fin matrices can span the expansion gap proximate the first manifold and the second manifold, but not span the entire gap between the first manifold and second manifold. Using finite element analysis, it has been predicted that a probable result from using partial fin matrices of about 10 fins proximate the first manifold in two expansion gaps can reduce thermal and mechanical stresses occurring in prior art heat exchangers by about 22%.

It will be appreciated that the foregoing description provides examples of the disclosed system and technique. However, it is contemplated that other implementations of the disclosure may differ in detail from the foregoing examples. All references to the disclosure or examples thereof are intended to reference the particular example being discussed at that point and are not intended to imply any limitation as to the scope of the disclosure more generally. All language of distinction and disparagement with respect to certain features is intended to indicate a lack of preference for those features, but not to exclude such from the scope of the disclosure entirely unless otherwise indicated.

Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context.

Accordingly, this disclosure includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the disclosure unless otherwise indicated herein or otherwise clearly contradicted by context. 

We claim:
 1. A heat exchanger comprising: a first manifold and a second manifold; a plurality of substantially parallelly aligned tubes having a first end and a second end, the plurality of tubes connected to the first manifold at the first end thereof and connected to the second manifold at the second end thereof such that fluid communication is established between the first manifold and the second manifold; a plurality of gaps disposed between adjacent tubes of the plurality of tubes; and a plurality of fin matrices, each of the plurality of fin matrices being formed from a plurality of fins, respective individual fin matrices of the plurality of fin matrices each spanning an individual gap of the plurality of gaps and extending from the first end to the second end of the plurality of tubes, respectively; wherein at least two adjacent tubes define at least one expansion gap that accommodates thermal expansion of the plurality of tubes.
 2. The heat exchanger of claim 1, wherein a portion of the at least one expansion gap adjacent to the first manifold is spanned by a partial fin matrix.
 3. The heat exchanger of claim 1, wherein portions of the at least one expansion gap adjacent to the first manifold and second manifold are only partially spanned by partial fin matrices.
 4. The heat exchanger of claim 1, wherein at least two sets of adjacent tubes define at least two expansion gaps.
 5. The heat exchanger of claim 1, further comprising a first tube set, a second tube set, and a third tube set, each tube set separated by one expansion gap, and at least a portion of the expansion gap is not spanned by a fin matrix.
 6. The heat exchanger of claim 5, wherein the first tube set, the second tube set, and the third tube set include substantially the same amount of tubes as each other.
 7. An internal combustion engine comprising a heat exchanger, the heat exchanger comprising: a first manifold and a second manifold; a plurality of tubes having a first end and a second end, the plurality of tubes connected to the first manifold at the first end and connected to the second manifold at the second end such that fluid communication is established between the first manifold and the second manifold; the plurality of tubes arranged parallel to and aligned with each other forming a plurality of gaps between adjacent tubes; and a plurality of fin matrices formed from a plurality of fins, the fin matrices spanning the plurality of gaps and extending from the first end to the second end of the plurality of tubes; wherein at least two adjacent tubes define at least one expansion gap that accommodates thermal expansion of the plurality of tubes.
 8. The internal combustion engine of claim 7, wherein a portion of the at least one expansion gap adjacent to the first manifold is spanned by a partial fin matrix.
 9. The internal combustion engine of claim 7, wherein portions of the at least one expansion gap adjacent to the first manifold and second manifold are spanned by partial fin matrices.
 10. The internal combustion engine of claim 7, wherein at least two sets of adjacent tubes define at least two expansion gaps.
 11. The internal combustion engine of claim 7, further comprising a first tube set, a second tube set, and a third tube set, each tube set separated by one expansion gap, and at least a portion of the expansion gap is not spanned by a fin matrix.
 12. The internal combustion engine of claim 11, wherein the first tube set, the second tube set, and the third tube set include substantially the same amount of tubes as each other.
 13. A method of manufacturing a heat exchanger, the method comprising: arranging a plurality of tubes parallel and aligned with each other forming a plurality of gaps between adjacent tubes; assembling a plurality of fin matrices in a plurality of the gaps formed between adjacent tubes; assembling at least one spacer in at least a portion of at least one gap; arranging the plurality of tubes between a first manifold and a second manifold such that fluid communication is created between the first manifold and the second manifold through the plurality of tubes; coating at least the fin matrices with a braze material; heating at least the braze material to at least a first predetermined temperature; and removing the at least one spacer from the at least one gap, forming at least one expansion gap defined by at least two adjacent tubes, the at least one expansion gap accommodating thermal expansion of the plurality of tubes.
 14. The method of manufacturing a heat exchanger of claim 13 further comprising allowing the braze material to cool to a second predetermined temperature.
 15. The method of manufacturing a heat exchanger of claim 13 further comprising assembling a partial fin matrix in the at least one gap in which the at least one spacer is assembled, the partial fin matrix adjacent to the first manifold.
 16. The method of manufacturing a heat exchanger of claim 13 further comprising assembling two partial fin matrices in the at least one gap in which the at least one spacer is assembled, the two partial fin matrices individually adjacent to the first manifold and second manifold.
 17. The method of manufacturing a heat exchanger of claim 13, wherein two spacers are assembled in two gaps formed between adjacent tubes.
 18. The method of manufacturing a heat exchanger of claim 13, wherein the at least one spacer assembled in the at least one gap is a made up of a plurality of fins.
 19. The method of manufacturing a heat exchanger of claim 13 further comprising assembling a first tube set, a second tube set, and a third tube set, each tube set separated by at least one expansion gap.
 20. The method of manufacturing a heat exchanger of claim 19, wherein the first tube set, second tube set, and third tube set include substantially the same amount of tubes as one other. 